The present invention relates to an electrical discharge wire-cutting machine, and more particularly to an electrical discharge wire-cutting machine having a means for detecting the remaining length of a wire electrode.
Japanese Laid-Open Patent Publication No. 60-197320 discloses an electrical discharge wire-cutting machine having a device for detecting the remaining length of a wire electrode. More specifically, when a new wire supply bobbin is installed in place, the operator sets the amount by which a wire electrode is wound on the wire supply bobbin. The device calculates and displays the remaining length of the wire electrode by subtracting the length consumed as an electrical discharge process progresses from the initial length of the wire electrode which is calculated from the value set by the operator.
The disclosed device, however, does not directly detect the remaining length of the wire electrode, but essentially detects the consumed length of the wire electrode. Therefore, the more the wire electrode is consumed and the smaller the remaining length become, the more detecting errors are accumulated, so that the calculated remaining length of the wire electrode is subjected to a greater error. The wire supply bobbin installed on the electrical discharge wire-cutting machine may not necessarily be brandnew, but may be a used wire supply bobbin. If a used wire supply bobbin is installed, its weight must be measured, and the initial amount by which the wire electrode is wound thereon must be set by the operator. This process is tedious and time consuming.